A projection television set typically includes three cathode ray tubes (CRTs), corresponding to the primary colors, red, blue and green. A projection lens assembly uses a plurality of lens to magnify the image appearing on the CRT faceplate and project that image onto a much larger viewing screen. CRTs used in projection televisions typically have a diameter of 3 to 9 inches. The image projected onto the screen generally has a size ranging from 40 to 60 inches or larger measured diagonally.
Each CRT has an associated magnifying lens system mounted adjacent to the CRT faceplate. Usually, the lens assembly is formed with at least one “A” lens element, at least one “B” lens element and at least one “C” lens element. Regardless of the number of lens elements, these are generally referred to in the art as “A”, “B” and “C” lens groups. That is, each “group” can be comprised of one or more lens elements. The “B” lens group usually includes a lens formed of glass, while the “A” and “C” lens groups can be formed of plastic. However, it should be understood that each group can include one or more lenses formed of glass and one or more lenses formed of plastic. Alternatively, the lens assemblies can include all glass lenses or all plastic lenses.
These lenses typically include a mounting flange attached to the lens. This flange can be masked to block unwanted light transmission through or near the flange. The mask can extend along the curve of the optic up to a place on the curve where light is allowed through the lens or “clear aperture”.
This mask can be painted onto the flange. However, drawbacks to painting on the mask include the need for an additional step for applying the mask and subsequent cleaning processes, the release of unwanted volatile organic components from the painting process, creation of hazardous waste from the painting and cleaning processes and difficulties with further processing steps, to list a few.